It is known in the art to co-extrude two separate doughs. Such a co-extruder is useful in forming an extrudate rope having a multi-texture dough, for example an outer dough having a crispy texture when baked, with the inner dough having a chewy and moist texture after baking.
The prior art has not, however, solved the problem of providing an extruded rope composed of three separate materials, for example three separate doughs, including an inner-most core, which inner-most core is surrounded by an intermediate layer, which in turn is surrounded by a third layer.
Examples of types of apparatus for forming a co-extruded product include the following.
For example, U.S. Pat. Nos. 4,113,819, 4,266,920 and 4,416,910, all to Hayashi, describe apparatus and processes for manufacturing multi-layered dough materials comprising layers of dough and fat or oil, such as butter. These processes involve co-extrusion of dough and fat through a die having concentric annular orifices to form a hollow tube in which an inner layer of fat is surrounded by an outer layer of dough. In U.S. Pat. Nos. 4,413,819 and 4,416,910, this tube is then collapsed under its own weight on to a first conveyor, which passes it under a rolling assembly comprising a plurality of rolls which are themselves carried around an endless belt. At the end of the first conveyor, the rolled sheet passes downwardly to an oscillating chute, which oscillates parallel to the direction of motion of the first conveyor, and is formed into a pile, comprising multiple plies of the sheet, on a second conveyor, which conveys it under second rolling assembly generally similar to the first one already described.
In the apparatus shown in U.S. Pat. Nos. 4,113,819 and 4,416,910, both orifices of the co-extrusion die are annular. The patents discuss the possibility of using a die having orifices of flattened or rectangular form, but state that, since the elevation angles of various portions of the inner faces of the nozzles are considerably different from each other because of the required changes in the cross-section of the channels used to feed material to the orifices of such a flattened die, such flattened or rectangular orifices are to be avoided because the discharge speed is different between the middle and end portions of the rectangular orifices. Such changes in discharge speed would result in non-uniformity of the thickness of the layers of fats and dough forming the co-extruded tube, and might result in distortion or rupture of the tube. Also, if in accordance with the teachings of these patents annular dies producing a hollow cylindrical tube are used, and if this tube is have the diameter desirable to produce a sheet of the desired width for high-speed production, the dies required are extremely large, cumbersome and expensive to form.
U.S. Pat. No. 3,572,259 to Hayashi discloses a process in which a cylinder of dough filled with a filler is co-extruded in the same manner as in U.S. Pat. No. 4,113,819, and the co-extruded cylinder is thereafter formed into double-layered spheres. A similar method, not restricted to the co-extrusion technique of U.S. Pat. No. 4,113,819, is disclosed in U.S. Pat. No. 3,351,026 to Hayashi.
Other types of devices for providing additional material to a co-extruded product, are discussed as follows.
Moreland, in U.S. Pat. No. 4,028,024 teaches manufacture of filled capsules using a co-extruder. The product formed by this co-extruder is a capsule having a medicament or edible substance encased in a casing formed of gelatin or dough. The capsule may be a single color or may have different colors on opposite sides of a single capsule. This two-colored capsule is formed in the extruder by using different colored materials in conduits 13,14 of the apparatus of FIG. 4. As seen in this figure, the core material enters through an orifice 61 surrounded by a body part 59 having inlet openings on opposite sides thereof. This permits entry of the two differently colored materials on opposite sides of the orifice 61, with a body part 69 causing merging of the inner and outer layers into a single co-extrudate body. While three conduits are provided, only two materials are taught, having a total of potentially three different colors. There is no teaching of an extrudate product having an inner core material, a second co-extrudate material surrounding the core material, and a third co-extrudate material surrounding the second co-extrudate material.
In U.S. Pat. No. 3,314,381 to Fries et al., an apparatus is shown for filling baked products. The "co-extrudate" product formed is in fact an extruded material forming the interior and the exterior material portions of the final extrudate product. A second material is injected into the body of the first material during extrusion thereof by a spiral-shaped member having a plurality of orifices therein, to release a second material in a spiral-shaped pattern into the first material. There is no teaching of an extrudate product having an inner core material, a second co-extrudate material surrounding the core material, and a third co-extrudate material surrounding the second co-extrudate material.
In particular, it is a problem in the art to prevent, in a co-extruded dough, "bleeding" between the inner-most dough layer and the enrobing dough layer which surrounds the inner-most dough layer. Furthermore, where such doughs are sufficiently different in the amount of moisture they contain, it is a problem to prevent moisture migration from, for example, the inner-most dough layer to the enrobing dough layer.